Vibrato is pitch based and Tremolo is amplitude based, you are correct.
Vibrato is usually achieved (nowadays) with a slight delay (say about 4ms) with no dry signal and the delay being modulated slightly, usually at a fast rate. This is how the Boss VB-2 does it. You can do it with almost any digital delay with modulation.
Older vibratos, like in Magnatone amps, accomplish their jobs by using phase shift. You can get a similar effect with a phasor, but removing the dry signal (hey try this experiment: run a signal through two channels, one with a phasor on it, and the other dry. Flip the phase on the dry one and it should cancel the dry signal and leave you with a vibrato)
Anyway, the Chicken Salad vibrato is a Univibe type pedal. Not bad for cheap.
My favorite Tremolos are:
Boss PN-2 for versatility and cool machine gun sound
Dunlop Trem for sturdiness
Fulltone Supatrem for fatness of tone.
Demeter Tremulator for awesomeness.
Guyatone Flip for grooviness
Kay Tremolo in all it's blue plastic glory for rapid stutter and coolness.
Danelectro Tuna Melt for cheapness and still great sound.
Carl Martin Tremo O Vibe for lusciousness
E-H Pulsar (the new one) for cool on the cheap.
Mooger Fooger Ring Modulator - one of the coolest tremolos out there.
The King Trem is a very expensive cool sounding vibratoey Trem. Kind of like the old bias trem on a brownface fender.
It's easier to list the ones I don't like.